The liberation and metabolism of arachidonic acid (AA) from the cell membrane results in the generation of pro-inflammatory metabolites by several different pathways. Arguably, two of the most important pathways to inflammation are mediated by the enzymes 5-lipoxygenase (5-LO) and cyclooxygenase (COX). These parallel pathways result in the generation of leukotrienes and prostaglandins, respectively, which play important roles in the initiation and progression of the inflammatory response. These vasoactive compounds are chemotaxins, which promote infiltration of inflammatory cells into tissues and serve to prolong the inflammatory response. Consequently, the enzymes responsible for generating these mediators of inflammation have become the targets for many new drugs aimed at the treatment of inflammation that contributes to the pathogenesis of diseases such as rheumatoid arthritis, osteoarthritis, Alzheimer's disease and certain types of cancer.
Inhibition of the cyclooxygenase (COX) enzyme is the mechanism of action attributed to most nonsteroidal anti-inflammatory drugs (NSAIDS). There are two distinct isoforms of the COX enzyme (COX-1 and COX-2) that share approximately 60% sequence homology, but differ in expression profiles and function. COX-1 is a constitutive form of the enzyme that has been linked to the production of physiologically important prostaglandins involved in the regulation of normal physiological functions such as platelet aggregation, protection of cell function in the stomach and maintenance of normal kidney function (Dannhardt and Kiefer (2001) Eur. J. Med. Chem. 36:109-26). The second isoform, COX-2, is a form of the enzyme that is inducible by pro-inflammatory cytokines such as interleukin-1β (IL-1β) and other growth factors (Herschmann (1994) Cancer Metastasis Rev. 134:241-56; Xie et al. (1992) Drugs Dev. Res. 25:249-65). This isoform catalyzes the production of prostaglandin E2 (PGE2) from AA. Inhibition of COX-2 is responsible for the anti-inflammatory activities of conventional NSAIDs.
Inhibitors that demonstrate dual specificity for COX-2 and 5-LO, while maintaining COX-2 selectivity relative to COX-1, would have the obvious benefit of inhibiting multiple pathways of AA metabolism. Such inhibitors would block the inflammatory effects of PGE2, as well as, those of multiple leukotrienes (LT) by limiting their production. This includes the vasodilation, vasopermeability and chemotactic effects of LTB4 and LTD4 and the effects of LTE4, also known as the slow reacting substance of anaphalaxis. Of these, LTB4 has the most potent chemotactic and chemokinetic effects (Moore (1985) in Prostanoids: Pharmacological, Physiological and Clinical Relevance, Cambridge University Press, N.Y., pp. 229-30) and has been shown to be elevated in the gastrointestinal mucosa of patients with inflammatory bowel disease (Sharon and Stenson (1983) Gastroenterology 84:1306-13) and within the synovial fluid of patients with rheumatoid arthritis (Klicksein et al. (1980) J. Clin. Invest. 66:1166-70; Rae et al. (1982) Lancet ii:1122-4).
In addition to the above-mentioned benefits of dual COX-2/5-LO inhibitors, many dual inhibitors do not cause some of the side effects that are typical of NSAIDs or COX-2 inhibitors, including the gastrointestinal damage and discomfort caused by traditional NSAIDs. It has been suggested that NSAID-induced gastric inflammation is largely due to metabolites of 5-LO, particularly LTB4, which attracts cells to the site of a gastric lesion thus causing further damage (Kircher et al. (1997) Prostaglandins Leukot. Essent. Fatty Acids 56:417-23). Leukotrienes represent the primary AA metabolites within the gastric mucosa following prostanoid inhibition. It appears that these compounds contribute to a significant amount of the gastric epithelial injury resulting from the use of NSAIDs. (Celotti and Laufer (2001) Pharmacol. Res. 43:429-36). Dual inhibitors of COX-2 and 5-LO were also demonstrated to inhibit the coronary vasoconstriction in arthritic hearts in a rat model (Gok et al (2000) Pharmacology 60:41-46). Taken together, these characteristics suggest that there may be distinct advantages to dual inhibitors of COX-2 and 5-LO over specific COX-2 inhibitors and non-specific NSAIDs with regard to both increased efficacy and reduced side effects.
Because the mechanism of action of COX inhibitors overlaps that of most conventional NSAIDs, COX inhibitors are used to treat many of the same symptoms, such as the pain and swelling associated with inflammation in transient conditions and chronic diseases in which inflammation plays a critical role. Transient conditions include the treatment of inflammation associated with minor abrasions, sunburn or contact dermatitis, as well as, the relief of pain associated with tension and migraine headaches and menstrual cramps. Chronic conditions include arthritic diseases such as rheumatoid arthritis and osteoarthritis. Although rheumatoid arthritis is largely an autoimmune disease and osteoarthritis is caused by the degradation of cartilage in joints, reducing the inflammation associated with each provides a significant increase in the quality of life for those suffering from these diseases (Wienberg (2001) Immunol. Res. 22:319-41; Wollhiem (2000) Curr. Opin. Rheum. 13:193-201). As inflammation is a component of rheumatic diseases in general, the use of COX inhibitors has been expanded to include diseases such as systemic lupus erythromatosus (SLE) (Goebel et al. (1999) Chem. Res. Tox. 12:488-500; Patrono et al. (1985) J. Clin. Invest. 76:1011-1018) and rheumatic skin conditions such as scleroderma. COX inhibitors are also used for the relief of inflammatory skin conditions that are not of rheumatic origin, such as psoriasis, in which reducing the inflammation resulting from the over production of prostaglandins could provide a direct benefit (Fogh et al. (1993) Acta Derm. Venereol (Oslo) 73:191-3).
In addition to their use as anti-inflammatory agents, another potential role for COX inhibitors is the treatment of cancer. Over-expression of COX-2 has been demonstrated in various human malignancies and inhibitors of COX-2 have been shown to be efficacious in the treatment of animals with skin, breast and bladder tumors. While the mechanism of action is not completely understood, the over-expression of COX-2 has been shown to inhibit apoptosis and increase the invasiveness of tumorgenic cell types (Dempke et al. (2001) J. Can. Res. Clin. Oncol. 127:411-17; Moore and Simmons (2000) Current Med. Chem. 7:1131-44). It is possible that enhanced production of prostaglandins, resulting from the over-expression of COX-2, promotes cellular proliferation and consequently increases angiogenesis. (Moore (1985) in Prostanoids: Pharmacological, Physiological and Clinical Relevance, Cambridge University Press, N.Y., pp. 229-30; Fenton et al. (2001) Am. J. Clin. Oncol. 24:453-57).
There have been a number of clinical studies evaluating COX-2 inhibitors for potential use in the prevention and treatment of different types of cancer. In 1999, 130,000 new cases of colorectal cancer were diagnosed in the United States. Aspirin, a non-specific NSAID, has been found to reduce the incidence of colorectal cancer by 40-50% (Giovannucci et al. (1995) N. Engl. J. Med. 333:609-614) and mortality by 50% (Smalley et al. (1999) Arch. Intern. Med. 159:161-166). In 1999, the FDA approved the COX-2 inhibitor celecoxib for use in FAP (Familial Ademonatous Polyposis) to reduce colorectal cancer mortality. It is believed that other cancers with evidence of COX-2 involvement may be successfully prevented and/or treated with COX-2 inhibitors including, but not limited to, esophageal cancer, head and neck cancer, breast cancer, bladder cancer, cervical cancer, prostate cancer, hepatocellular carcinoma and non-small cell lung cancer (Jaeckel et al. (2001) Arch. Otolarnygol. 127:1253-59; Kirschenbaum et al. (2001) Urology 58:127-31; Dannhardt and Kiefer (2001) Eur. J. Med. Chem. 36:109-26). COX-2 inhibitors may also prove successful in preventing colon cancer in high-risk patients. There is also evidence that COX-2 inhibitors can prevent or even reverse several types of life-threatening cancers. To date, as many as fifty studies show that COX-2 inhibitors can prevent pre-malignant and malignant tumors in animals, and possibly prevent bladder, esophageal and skin cancers as well. COX-2 inhibition could prove to be one of the most important preventive medical accomplishments of the century.
Recent scientific progress has identified correlations between COX-2 expression, general inflammation and the pathogenesis of Alzheimer's Disease (AD) (Ho et al. (2001) Arch. Neurol. 58:487-92). In animal models, transgenic mice that over-express the COX-2 enzyme have neurons that are more susceptible to damage. The National Institute on Aging (NIA) is launching a clinical trial to determine whether NSAIDs can slow the progression of Alzheimer's disease. Naproxen (a non-selective NSAID) and rofecoxib (Vioxx, a COX-2 specific selective NSAID) will be evaluated. Previous evidence has indicated that inflammation contributes to Alzheimer's disease. According to the Alzheimer's Association and the NIA, about 4 million people suffer from AD in the United States and this is expected to increase to 14 million by mid-century.
The COX enzyme (also known as prostaglandin H2 synthase) catalyzes two separate reactions. In the first reaction, AA is metabolized to form the unstable prostaglandin G2 (PGG2), a cyclooxygenase reaction. In the second reaction, PGG2 is converted to the endoperoxide PGH2, a peroxidase reaction. The short-lived PGH2 non-enzymatically degrades to PGE2. The compounds described herein are the result of a discovery strategy that combined an assay focused on the inhibition of COX-1 and COX-2 peroxidase activity with a chemical dereplication process to identify novel inhibitors of the COX enzymes.
The term gene expression is often used to describe the broad result of mRNA production and protein synthesis. In fact, changes in actual gene expression may never result in observable changes on the protein level. The corollary, that changes in protein level do not always result from changes in gene expression, can also be true. There are six possible points of regulation in the pathway leading from genomic DNA to a functional protein: (1) transcriptional regulation by nuclear factors and other signals leading to production of pre-mRNA; (2) pre-mRNA processing regulation involving exon splicing, the additions of a 5′ cap structure and 3′ poly-adenylation sequence and transport of the mature mRNA from the nucleus into the cytoplasm; (3) mRNA transport regulation controlling localization of the mRNA to a specific cytoplasmic site for translation into protein; (4) mRNA degradation regulation controlling the size of the mRNA pool either prior to any protein translation or as a means of ending translation from that specific mRNA; (5) translational regulation of the specific rate of protein translation initiation and (6) post-translation processing regulation involving modifications such as glycosylation and proteolytic cleavage. In the context of genomics research it is important to use techniques that measure gene expression levels closer to the initial steps (e.g. mRNA levels) rather than later steps (e.g. protein levels) in this pathway.
Recent reports have addressed the possible involvement of flavonoids, isolated from the medicinal herb Scutellaria baicalensis, in alterations in cox-2 gene expression (Wakabayashi and Yasui (2000) Eur. J. Pharmacol. 406:477-481; Chen et al. (2001) Biochem. Pharmacol. 61:1417-1427; Chi et al. (2001) 61:1195-1203 and Raso et al. (2001) Life Sci. 68:921-931). Each of above cited studies on cox-2 gene expression used a Western Blot technique to evaluate putative alterations in gene expression without validation on the molecular level. Since this method only measures protein levels and not the specific transcription product, mRNA, it is possible that other mechanisms are involved leading to the observed increase in protein expression. For example, LPS has been reported to modulate mRNA half-lives via instability sequences found in the 3′ untranslated region (3′UTR) of mRNAs (Watkins et al. (1999) Life Sci. 65:449-481), which could account for increased protein expression without alternations in the rate of gene transcription. Consequently, this leaves open the question of whether or not these treatment conditions resulted in a meaningful change in gene expression.
Techniques, such as RT-qPCR and DNA microarray analysis, rely on mRNA levels for analysis and can be used to evaluate levels of gene expression under different conditions, i.e. in the presence or absence of a pharmaceutical agent. There are no known reports using techniques that specifically measure the amount of mRNA, directly or indirectly, in the literature when Free-B-ring flavonoids or flavans are used as the therapeutic agents.
Flavonoids are a widely distributed group of natural products. The intake of flavonoids has been demonstrated to be inversely related to the risk of incident dementia. The mechanism of action, while not known, has been speculated as being due to the anti-oxidative effects of flavonoids (Commenges et al. (2000) Eur. J. Epidemiol. 16:357-363). Polyphenol flavones induce programmed cell death, differentiation and growth inhibition in transformed colonocytes by acting at the mRNA level on genes including cox-2, Nuclear Factor kappa B (NFκB) and bcl-X(L) (Wenzel et al. (2000) Cancer Res. 60:3823-3831). It has been reported that the number of hydroxyl groups on the B ring is important in the suppression of cox-2 transcriptional activity (Mutoh et al. (2000) Jnp. J. Cancer Res. 91:686-691).
Free-B-ring flavones and flavonols are a specific class of flavonoids, which have no substituent groups on the aromatic B ring (referred to herein as Free-B-ring flavonoids), as illustrated by the following general structure:
wherein                R1, R2, R3, R4, and R5 are independently selected from the group consisting of —H, —OH, —SH, OR, —SR, —NH2, —NHR, —NR2, —NR3+X−, a carbon, oxygen, nitrogen or sulfur, glycoside of a single or a combination of multiple sugars including, but not limited to aldopentoses, methyl-aldopentose, aldohexoses, ketohexose and their chemical derivatives thereof;wherein        R is an alkyl group having between 1-10 carbon atoms; and        X is selected from the group of pharmaceutically acceptable counter anions including, but not limited to hydroxyl, chloride, iodide, sulfate, phosphate, acetate, fluoride, carbonate, etc.        
Free-B-ring flavonoids are relatively rare. Out of 9,396 flavonoids synthesized or isolated from natural sources, only 231 Free-B-ring flavonoids are known (The Combined Chemical Dictionary, Chapman & Hall/CRC, Version 5:1 June 2001). Free-B-ring flavonoids have been reported to have diverse biological activity. For example, galangin (3,5,7-trihydroxyflavone) acts as an anti-oxidant and free radical scavenger and is believed to be a promising candidate for anti-genotoxicity and cancer chemoprevention. (Heo et al. (2001) Mutat. Res. 488:135-150). It is an inhibitor of tyrosinase monophenolase (Kubo et al. (2000) Bioorg. Med. Chem. 8:1749-1755), an inhibitor of rabbit heart carbonyl reductase (Imamura et al. (2000) J. Biochem. 127:653-658), has antimicrobial activity (Afolayan and Meyer (1997) Ethnopharmacol. 57:177-181) and antiviral activity (Meyer et al. (1997) J. Ethnopharmacol. 56:165-169). Baicalein and two other Free-B-ring flavonoids, have antiproliferative activity against human breast cancer cells. (So et al. (1997) Cancer Lett. 112:127-133).
Typically, flavonoids have been tested for activity randomly based upon their availability. Occasionally, the requirement of substitution on the B-ring has been emphasized for specific biological activity, such as the B-ring substitution required for high affinity binding to p-glycoprotein (Boumendjel et al. (2001) Bioorg. Med. Chem. Lett. 11:75-77); cardiotonic effect (Itoigawa et al. (1999) J. Ethnopharmacol. 65: 267-272), protective effect on endothelial cells against linoleic acid hydroperoxide-induced toxicity (Kaneko and Baba (1999) Biosci. Biotechnol. Biochem. 63:323-328), COX-1 inhibitory activity (Wang (2000) Phytomedicine 7:15-19) and prostaglandin endoperoxide synthase activity (Kalkbrenner et al. (1992) Pharmacology 44:1-12). Only a few publications have mentioned the significance of the unsubstituted B-ring of the Free-B-ring flavonoids. One example is the use of 2-phenyl flavones, which inhibit NADPH quinone acceptor oxidoreductase, as potential anticoagulants (Chen et al. (2001) Biochem. Pharmacol. 61:1417-1427).
The reported mechanism of action with respect to the anti-inflammatory activity of various Free-B-ring flavonoids has been controversial. The anti-inflammatory activity of the Free-B-ring flavonoids, chrysin (Liang et al. (2001) FEBS Lett. 496:12-18), wogonin (Chi et al. (2001) Biochem. Pharmacol. 61:1195-1203) and halangin (Raso et al. (2001) Life, Sci. 68:921-931) has been associated with the suppression of inducible cyclooxygenase and nitric oxide synthase via activation of peroxisome-proliferator activated receptor gamma (PPARγ) and influence on degranulation and AA release (Tordera et al. (1994) Z. Naturforsch [C] 49:235-240). It has been reported that oroxylin, baicalein and wogonin inhibit 12-lipoxygenase activity without affecting cyclooxygenases (You et al. (1999) Arch. Pharm. Res. 22:18-24). More recently, the anti-inflammatory activity of wogonin, baicalin and baicalein has been reported as occurring through inhibition of inducible nitric oxide synthase and cox-2 enzyme production induced by nitric oxide inhibitors and lipopolysaccharides (Chen et al. (2001) Biochem. Pharmacol. 61:1417-1427). It has also been reported that oroxylin acts via suppression of NFκB activation (Chen et al. (2001) Biochem. Pharmacol. 61:1417-1427). Finally, wogonin reportedly inhibits inducible PGE2 production in macrophages (Wakabayashi and Yasui (2000) Eur. J. Pharmacol. 406:477-481).
Inhibition of the phosphorylation of mitogen-activated protein kinase (MAPK) and inhibition of Ca2+ ionophore A23187 induced PGE2 release by baicalein has been reported as the mechanism of anti-inflammatory activity of Scutellariae radix (Nakahata et al. (1999) Nippon Yakurigaku Zasshi 114, Supp. 11:215P-219P; Nakahata et al. (1998) Am. J. Chin. Med. 26:311-323). Baicalin from Scutellaria baicalensis reportedly inhibits superantigenic staphylococcal exotoxins stimulated T-cell proliferation and production of IL-1β, IL-6, tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ) (Krakauer et al. (2001) FEBS Lett. 500:52-55). Thus, the anti-inflammatory activity of baicalin has been associated with inhibiting the pro-inflammatory cytokines mediated signaling pathways activated by superantigens. However, it has also been proposed that the anti-inflammatory activity of baicalin is due to the binding of a variety of chemokines, which limit their biological activity (Li et al. (2000) Immunopharmacol. 49:295-306). Recently, the effects of baicalin on adhesion molecule expression induced by thrombin and thrombin receptor agonist peptide (Kimura et al. (2001) Planta Med. 67:331-334), as well as, the inhibition of MAPK cascade (Nakahata et al. (1999) Nippon Yakurigaku Zasshi 114, Supp 11:215P-219P; Nakahata et al. (1998) Am. J. Chin Med. 26:311-323) have been reported.
The Chinese medicinal plant Scutellaria baicalensis contains significant amounts of Free-B-ring flavonoids, including baicalein, baicalin, wogonin and baicalenoside. Traditionally, this plant has been used to treat a number of conditions including clearing away heat, purging fire, dampness-warm and summer fever syndromes; polydipsia resulting from high fever; carbuncle, sores and other pyogenic skin infections; upper respiratory infections such as acute tonsillitis, laryngopharyngitis and scarlet fever; viral hepatitis; nephritis; pelvitis; dysentery; hematemesis and epistaxis. This plant has also traditionally been used to prevent miscarriage (see Encyclopedia of Chinese Traditional Medicine, ShangHai Science and Technology Press, ShangHai, China, 1998). Clinically, Scutellaria is now used to treat conditions such as pediatric pneumonia, pediatric bacterial diarrhea, viral hepatitis, acute gallbladder inflammation, hypertension, topical acute inflammation resulting from cuts and surgery, bronchial asthma and upper respiratory infections (Encyclopedia of Chinese Traditional Medicine, ShangHai Science and Technology Press, ShangHai, China, 1998). The pharmacological efficacy of Scutellaria roots for treating bronchial asthma is reportedly related to the presence of Free-B-ring flavonoids and their suppression of eotaxin associated recruitment of eosinophils (Nakajima et al. (2001) Planta Med. 67(2):132-135).
To date, a number of naturally occurring Free-B-ring flavonoids have been commercialized for varying uses. For example, liposome formulations of Scutellaria extracts have been utilized for skin care (U.S. Pat. Nos. 5,643,598; 5,443,983). Baicalin has been used for preventing cancer due to its inhibitory effects on oncogenes (U.S. Pat. No. 6,290,995). Baicalin and other compounds have been used as antiviral, antibacterial and immunomodulating agents (U.S. Pat. No. 6,083,921) and as natural anti-oxidants (Poland Pub. No. 9,849,256). Chrysin has been used for its anxiety reducing properties (U.S. Pat. No. 5,756,538). Anti-inflammatory flavonoids are used for the control and treatment of anorectal and colonic diseases (U.S. Pat. No. 5,858,371) and inhibition of lipoxygenase (U.S. Pat. No. 6,217,875). These compounds are also formulated with glucosamine collagen and other ingredients for repair and maintenance of connective tissue (U.S. Pat. No. 6,333,304). Flavonoid esters constitute the active ingredients for cosmetic compositions (U.S. Pat. No. 6,235,294). U.S. application Ser. No. 10/091,362, filed Mar. 1, 2002, entitled “Identification of Free-B-ring Flavonoids as Potent COX-2 Inhibitors,” discloses a method for inhibiting the cyclooxygenase enzyme COX-2 by administering a composition comprising a Free-B-ring flavonoid or a composition containing a mixture of Free-B-ring flavonoids to a host in need thereof. This is the first report of a link between Free-B-ring flavonoids and COX-2 inhibitory activity. This application is specifically incorporated herein by reference in its entirety.
Japanese Pat. No. 63027435, describes the extraction, and enrichment of baicalein and Japanese Pat. No. 61050921 describes the purification of baicalin.
Flavans include compounds illustrated by the following general structure:
wherein                R1, R2, R3, R4 and R5 are independently selected from the group consisting of —H, —OH, —SH, —OCH3, —SCH3, —OR, —SR, —NH2, —NRH, —NR2, —NR3+X−, esters of the mentioned substitution groups, including, but not limited to, gallate, acetate, cinnamoyl and hydroxyl-cinnamoyl esters, trihydroxybenzoyl esters and caffeoyl esters, and their chemical derivatives thereof; a carbon, oxygen, nitrogen or sulfur glycoside of a single or a combination of multiple sugars including, but not limited to, aldopentoses, methyl aldopentose, aldohexoses, ketohexose and their chemical derivatives thereof, dimer, trimer and other polymerized flavans;wherein        R is an alkyl group having between 1-10 carbon atoms; and        X is selected from the group of pharmaceutically acceptable counter anions including, but not limited to hydroxyl, chloride, iodide, sulfate, phosphate, acetate, fluoride, and carbonate, etc.        
Catechin is a flavan, found primarily in Acacia, having the following structure
Catechin works both alone and in conjunction with other flavonoids found in tea, and has both antiviral and antioxidant activity. Catechin has been shown to be effective in the treatment of viral hepatitis. It also appears to prevent oxidative damage to the heart, kidney, lungs and spleen and has been shown to inhibit the growth of stomach cancer cells.
Catechin and its isomer epicatechin inhibit prostaglandin endoperoxide synthase with an IC50 value of 40 μM. (Kalkbrenner et al. (1992) Pharmacol. 44:1-12). Five flavan-3-ol derivatives, including (+)-catechin and gallocatechin, isolated from the four plant species, Atuna racemosa, Syzygium carynocarpum, Syzygium malaccense and Vantanea peruviana, exhibit equal to or weaker inhibitory activity against COX-2, relative to COX-1, with IC50 values ranging from 3.3 μM to 138 μM (Noreen et al. (1998) Planta Med. 64:520-524). (+)-Catechin, isolated from the bark of Ceiba pentandra, inhibits COX-1 with an IC50 value of 80 μM (Noreen et al. (1998) J. Nat. Prod. 61:8-12). Commercially available pure (+)-catechin inhibits COX-1 with an IC50 value of around 183 to 279 μM, depending upon the experimental conditions, with no selectivity for COX-2 (Noreen et al. (1998) J. Nat. Prod. 61:1-7).
Green tea catechin, when supplemented into the diets of Sprague dawley male rats, lowered the activity level of platelet PLA2 and significantly reduced platelet cyclooxygenase levels (Yang et al. (1999) J. Nutr. Sci. Vitaminol. 45:337-346). Catechin and epicatechin reportedly weakly suppress cox-2 gene transcription in human colon cancer DLD-1 cells (IC50=415.3 μM) (Mutoh et al. (2000) Jpn. J. Cancer Res. 91:686-691). The neuroprotective ability of (+)-catechin from red wine results from the antioxidant properties of catechin, rather than inhibitory effects on intracellular enzymes, such as cyclooxygenase, lipoxygenase or nitric oxide synthase (Bastianetto et al. (2000) Br. J. Pharmacol. 131:711-720). Catechin derivatives purified from green tea and black tea, such as epigallocatechin-3-gallate (EGCG), epigallocatechin (EGC), epicatechin-3-gallate (ECG) and theaflavins showed inhibition of cyclooxygenase- and lipoxygenase-dependent metabolism of AA in human colon mucosa and colon tumor tissues (Hong et al. (2001) Biochem. Pharmacol. 62:1175-1183) and induced cox-2 gene expression and PGE2 production (Park et al. (2001) Biochem. Biophys. Res. Commun. 286:721-725). Epiafzelechin isolated from the aerial parts of Celastrus orbiculatus exhibited dose-dependent inhibition of COX-1 activity with an IC50 value of 15 μM and also demonstrated anti-inflammatory activity against carrageenin-induced mouse paw edema following oral administration at a dosage of 100 mg/kg (Min et al. (1999) Planta Med. 65:460-462).
Catechin and its derivatives from various plant sources, especially from green tea leaves, have been used in the treatment of HPV infected Condyloma acuminata (Cheng, U.S. Pat. No. 5,795,911) and in the treatment of hyperplasia caused by papilloma virus (Cheng, U.S. Pat. Nos. 5,968,973 and 6,197,808). Catechin and its derivatives have also been used topically to inhibit angiogenesis in mammalian tissue, in conditions such as skin cancer, psoriasis, spider veins or under eye circles (Anderson, U.S. Pat. No. 6,248,341), against UVB-induced tumorigenesis in mice (Agarwal et al. (1993) Photochem. Photobiol. 58:695-700), for inhibiting nitric oxide synthase at the level of gene expression and enzyme activity (Chan, U.S. Pat. No. 5,922,756), and as hair-growing agents (Takahashi, U.S. Pat. No. 6,126,940). Catechin-based compositions have also been formulated with other extracts and vitamins for treatment of acne (Murad, U.S. Pat. No. 5,962,517), hardening the tissue of digestive organs (Shi, U.S. Pat. No. 5,470,589) and for inhibiting 5 alpha-reductase activity in treating androgenic disorder related diseases and cancers (Liao, U.S. Pat. No. 5,605,929). Green tea extract has been formulated with seven other plant extracts for reducing inflammation by inhibiting the COX-2 enzyme, without identification of any of the specific active components (Mewmark, U.S. Pat. No. 6,264,995).
Acacia is a genus of leguminous trees and shrubs. The genus Acacia includes more than 1,000 species belonging to the family of Leguminosae and the subfamily of Mimosoideae. Acacias are distributed worldwide in places such as tropical and subtropical areas of Central and South America, Africa, parts of Asia, as well as, Australia, which has the largest number of endemic species. Acacias are present primarily in dry and arid regions where the forests are often in the nature of open thorny shrubs. The genus Acacia is divided into 3 subgenera based mainly on leaf morphology—Acacia, Aculiferum and Heterophyllum. Based on the nature of the leaves of mature trees, however, the genus Acacia can be divided into two “popular” groups—the typical bipinnate-leaved species and the phyllodenous species. A phyllode is a modified petiole expanded into a leaf-like structure with no leaflets, an adaptation to xerophytic conditions. The typical bipinnate-leaved species are found primarily throughout the tropics, whereas the phyllodenous species occur mainly in Australia. More than 40 species of Acacia have been reported in India. Gamble in his book entitled Flora of Madras Presidency listed 23 native species for southern India, 15 of which are found in Tamil Nadu. Since that time, however, many new Acacia species have been introduced to India and approximately 40 species are now found in Tamil Nadu itself The indigenous species are primarily thorny trees or shrubs and a few are thorny stragglers, such as A. caesia, A. pennata and A. sinuata. Many species have been introduced from Africa and Australia, including A. mearnsii, A. picnantha and A. dealbata, which have bipinnate leaves and A. auriculiformis, A. holoserecia and A. mangium, which are phyllodenous species.
Acacias are very important economically, providing a source of tannins, gums, timber, fuel and fodder. Tannins, which are isolated primarily from the bark, are used extensively for tanning hides and skins. Some Acacia barks are also used for flavoring local spirits. Some indigenous species like A. sinuata also yield saponins, which are any of various plant glucosides that form soapy lathers when mixed and agitated with water. Saponins are used in detergents, foaming agents and emulsifiers. The flowers of some Acacia species are fragrant and used to make perfume. For example, cassie perfume is obtained from A. ferrugenea. The heartwood of many Acacias is used for making agricultural implements and also provides a source of firewood. Acacia gums find extensive use in medicine and confectionary and as sizing and finishing materials in the textile industry. Lac insects can be grown on several species, including A. nilotica and A. catechu. Some species have been used for forestation of wastelands, including A. nilotica, which can withstand some water inundation and a few such areas have become bird sanctuaries.
To date, approximately 330 compounds have been isolated from various Acacia species. Flavonoids, a type of water-soluble plant pigments, are the major class of compounds isolated from Acacias. Approximately 180 different flavonoids have been identified, 111 of which are flavans. Terpenoids are second largest class of compounds isolated from species of the Acacia genus, with 48 compounds having been identified. Other classes of compounds isolated from Acacia include, alkaloids (28), amino acids/peptides (20), tannins (16), carbohydrates (15), oxygen heterocycles (15) and aliphatic compounds (10). (Buckingham, in The Combined Chemical Dictionary, Chapman & Hall CRC, version 5:2, December 2001).
Phenolic compounds, particularly flavans are found in moderate to high concentrations in all Acacia species (Abdulrazak et al. (2000) J. Anim. Sci. 13:935-940). Historically, most of the plants and extracts of the Acacia genus have been utilized as astringents to treat gastrointestinal disorders, diarrhea, indigestion and to stop bleeding (Vautrin (1996) Universite Bourgogne (France) European abstract 58-01C:177; Saleem et al. (1998) Hamdard Midicus. 41:63-67). The bark and pods of A. arabica Willd. contain large quantities of tannins and have been utilized as astringents and expectorants (Nadkarni (1996) India Materia Medica, Bombay Popular Prakashan, pp. 9-17). Diarylpropanol derivatives, isolated from stem bark of A. tortilis from Somalia, have been reported to have smooth muscle relaxing effects (Hagos et al. (1987) Planta Med. 53:27-31, 1987). It has also been reported that terpenoid saponins isolated from A. victoriae have an inhibitory effect on dimethylbenz(a)anthracene-induced murine skin carcinogenesis (Hanausek et al. (2000) Proc. Am. Assoc. Can. Res. Annu. Mtg. 41:663) and induce apoptosis (Haridas et al. (2000) Proc. Am. Assoc. for Can. Res. Annu. Mtg. 41:600). Plant extracts from A. nilotica have been reported to have spasmogenic, vasoconstrictor and anti-hypertensive activity (Amos et al. (1999) Phytotherapy Research 13:683-685; Gilani et al. (1999) Phytotherapy Research 13:665-669), and antiplatelet aggregatory activity (Shah et al. (1997) Gen. Pharmacol. 29:251-255). Anti-inflammatory activity has been reported for A. nilotica. It was speculated that flavonoids, polysaccharides and organic acids were potential active components (Dafallah and Al-Mustafa (1996) Am. J. Chin. Med. 24:263-269). To date, the only reported 5-lipoxygenase inhibitor isolated from Acacia is a monoterpenoidal carboxamide (Seikine et al. (1997) Chem. Pharm. Bull. (Tokyo) 45:148-11).
Acacia gums have been formulated with other plant ingredients and used for ulcer prevention without identification of any of the active components (Fuisz, U.S. Pat. No. 5,651,987). Acacia gums have also been formulated with other plant ingredients and used to improve drug dissolution (Blank, U.S. Pat. No. 4,946,684), by lowering the viscosity of nutritional compositions (Chancellor, U.S. Pat. No. 5,545,411).
The extract from the bark of Acacia was patented in Japan for external use as a whitening agent (Abe, JP10025238), as a glucosyl transferase inhibitor for dental applications (Abe, JP07242555), as a protein synthesis inhibitor (Fukai, JP 07165598), as an active oxygen-scavenging agent for external skin preparations (Honda, JP 07017847, Bindra U.S. Pat. No. 6,1266,950), and as a hyaluronidase inhibitor for oral consumption to prevent inflammation, pollinosis and cough (Ogura, JP 07010768).
Review of the literature has revealed no human clinical applications using mixtures of Free-B-ring flavonoids and flavans for relief of pain or measuring biochemical clinical outcomes for osteoarthritis treatment. This report appears to be the first randomized, double blind, placebo controlled study of the safety and efficacy of these compounds in humans.